The prevailing theories about Atlantis are:

                        ~It's Fiction
                        ~It's an exaggeration based on the fall of the Minoan civilization and the destruction of
                          the island Thera
                        ~It was Real

                   Below you'll find a brief summary of each of the theories as well as key points either for or
                   against the theory. Although many people in each camp consider the case closed there is no
                   definitive proof for any theory. In the case of the "It's Fiction" theory it is essentially
                   impossible to definitively prove that it was fiction.

Fiction
 

                   This is the easiest answer - Atlantis is fiction. It was made up to suit the purposes of Plato's
                   dialogues.

                   For

                       ~Nothing to prove. Timaeus and Critias are simply stories.

                  Against

                        ~It is stated several times within the dialogues that the story is true
                        ~Parts about the impassable sea and the true continent on the other side of Atlantis tend
                          to indicate a more detailed knowledge that a fictional story

Thera & The Minoan Civilization
 

                   There are some compelling similarites between the destruction of Thera and the destruction of
                   Atlantis.....

                   For

                        ~The island of Thera, a volcanic island, was destroyed around 1500 BC by an
                          explosion which caused more than half of the island to sink into the sea.
                        ~Artifacts found on the island indicate a sophisticated culture, probably part of the
                          Minoan Civilization.
                        ~There is evidence pointing to trade between the Minoans and Egyptians. The Egyptians
                          would certainly have been aware of the destruction or at least the tremedous damage
                          done to one of their trading partners.

                   Against

                        ~Proponents of this theory claim that Plato's date of 9000 years ago should really have
                          been 900 years ago: somewhere along the line either Solon or Plato made a mistake. If
                          the story was 900 years ago it would place Atlantis in the time frame of the Minoan
                          civilization on Crete and Thera. Conveniently overlooked in this thinking is that in
                          Timaeus the priest tells Solon that ancient Athens and Atlantis preceeded Egypt by a
                          thousand years. Egypt however existed and was known to have existed since long
                          before 1500 BC, the time of Crete and Thera. The times just don't add up unless you
                          assume the Egyptian priest was ignorant of his own recorded history.

It Existed
 

                   For

                        ~Plato says it's a true story.
 
                    Against

                        ~There are no other records of such a civlization existing.
                        ~Current archaeological evidence does not support the premise that such sophisticated
                          civilizations existed around 9000 BC anywhere in the world.